Citizens United fever: The debate over the controversial Supreme Court ruling continues. Curious how it could be undone? Check out our DIY guide to ditching the ruling. For more details, iWatch News reports on the argument over whether a constitutional amendment is the best way to overturn it.MoJo‘s Andy Kroll explores whether Sen. John McCain (R-Ariz.), who just asked Supreme Court to reconsider its decision, is reclaiming his status as a campaign-finance reformer. Meanwhile, dark-money fans are lining up to tell the court not to touch Citizens United.

McCarthy’s new ad, though, strikes a far softer tone. It repeatedly uses the word “change” and breaks from the attack-ad norm by employing professional actors.

Oppo-research group targets Dems: Andy Kroll reports on Media Tracker, a “nonpartisan” opposition-research group founded by to dig up dirt on Democrats that can be used in attack ads. “I’m talking about creating long-lasting impact for the conservative movement,” says its founder, a former Republican National Committee staffer. Meanwhile, the Obama campaign has a sophisticated ad shop ready to fight back against the likes of Media Trackers, Slate‘s Sasha Issenberg reports.

Where are the liberal megadonors? Also at Slate, Dave Weigel takes a look at why the super-PAC-fueled ideological purging of unworthy GOP candidates isn’t happening on the left. As Michael Vachon, spokesman for conservatives’ favorite boogeyman George Soros, explains, “The reason there’s not a Club for Growth-like organization on the left is that there is a greater diversity of views in the Democratic Party than there is in the Republican Party. There’s less of a hierarchically enforced ideological structure.”

Super-PACs keep the money flowing to state races:The Sunlight Foundation’s Anupama Narayanswamy reports that super-PACs spent nearly $1 million ahead of Tuesday’s primaries in Arkansas and Kentucky. A 21-year-old millionaire’s pro-Ron Paul super-PAC provided the majority of the $766,000 in outside spending that propelled Republican congressional candidate Thomas Massie to victory in the Bluegrass State. (MoJo‘s Tim Murphy has more his group here. Watch a campaign ad below.) Meanwhile, real-estate interests have spent a “mind boggling” $700,000 attempting to oust a 14-year incumbent in a Republican House primary in California.